The present invention relates to telechelic polymers and methods for making the same. More particularly, the present invention relates to telechelic polymer segments of controlled molecular weight having crosslinkable end groups and methods for preparing the same.
Telechelic polymers can be simply defined as polymers that bear reactive functional groups at their chain termini. The interest in these polymeric materials is derived from the fact that through these reactive end groups, a vast number of macromolecular materials can be prepared. Telechelic polymers have found application in the synthesis of block copolymers, star polymers, cross-linked polymer networks, and ionic polymer networks. Low molecular weight liquid telechelic polymers have been successfully used in reaction injection molding, and the formation of ABA triblock and multiblock copolymers via telechelic polymers has dramatically impacted the development of thermoplastic elastomers. Based on these numerous valuable applications, considerable research efforts have been devoted to improving the synthesis of telechelic polymers.
The development of telechelic polymers with crosslinkable end groups such as methacrylate or epoxide groups is of interest for the preparation of interpenetrating polymer networks, AB cross-linked polymeric materials, more thermally and chemically resistant materials, and for the immobilization of biomaterials. However, these reactive end groups have been typically incorporated through a post-polymerization transformation due to the instability of these functional groups to tolerate many of the typical conditions associated with polymerization reactions.
Recently, a non-metathesis-mediated polymer degradation approach was applied to polymers derived from ROMP. Copolymerization of cyclooctadiene (xe2x80x9cCODxe2x80x9d) with either cis-4,7-dihydro-1,3-dioxepan (1) or cis-4,7-dihydro-2-phenyl-1,3-dioxepan (2) using well-defined ruthenium-based metathesis initiators, (PCy3)Cl2Ruxe2x95x90CHRxe2x80x2 (wherein Rxe2x80x2=Ph (3)or wherein Rxe2x80x2=(CHxe2x95x90CPh2)(4)), resulted in a polymer bearing both poly(butadiene) and acetal units along the backbone. Subsequent acid hydrolysis of these acetal units resulted in the desired hydroxytelechelic poly(butadiene) (xe2x80x9cHTPBDxe2x80x9d) oligomers in moderate yields. Although this method proved to be successful for the synthesis of HTPBD, this method is not generally applicable for the preparation of telechelic polymers with other functional end groups.
As a result, a need exists for methods for synthesizing telechelic polymers having a variety of end groups, particularly crosslinkable end groups and which does not require post-polymerization transformations for polymer functionalization.
The present invention relates to telechelic polymers having crosslinkable end groups of the formula 
and methods for preparing the same wherein n is an integer 
is an alkadienyl group; Y is an alkyl group; and Z is crosslinkable end group. In general , the inventive synthesis involves reacting a chain transfer agent having crosslinkable end groups with a cycloalkene in the presence of a ruthenium or osmium initiator of the formula 
wherein:
M is ruthenium or osmium;
X and X1 are independently any anionic ligand;
L and L1 are any neutral electron donor ligand;
R and R1 are each hydrogen or a substituted or unsubstituted substituent wherein the substituent is selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl.
In particularly preferred embodiments, the initiator is as described above wherein R is hydrogen, R1 is phenyl or (xe2x80x94CHxe2x95x90CPh2), X and X1 are both chloride, and L and L1 ligands are xe2x80x94P(cyclohexyl)3; the cycloalkene is cyclooctadiene; and the chain transfer agent is cis-2-butene-1,4-diol dimethacrylate or cis-2-butene-1,4-diol diglycidyl ether.